Penicillin is derived from a fungi named Penicillium. They are a group of Beta-lactam antibiotics, which are used in the treatment or prevention of bacterial infections originated by susceptible, particularly gram-positive, organisms. They are usually bactericidal in action.
Classification of Penicillin
Based upon Penicillin’s ability to execute or destroy bacterium and effectiveness (ranging from limited to extensive), they can be classified into following four classes.
Natural Penicillins (Penicillin V, Penicillin G, Benzathine, Procaine Penicillin)
In the penicillin family, antibiotics of natural penicillin class were the first innovative agents, which were launched for clinical purposes. The original structure of penicillin-G is the basis of natural Penicillins. Antibiotics from this particular class of Penicillin are mainly useful against gram (+) strains of staphylococci and streptococci and a few gram (-) bacteria (for example, meningococcus). Additionally, you need to know that Penicillin V is not only useful for anaerobic coverage in patients who are suffering infections of oral cavity, but also it is considered as the agent of choice for treating streptococcal pharyngitis.
Penicillinase-Resistant Penicillins (Oxacillin, Dicloxacillin, Cloxacillin, Methicillin, Nafcillin)
The first drug of this class was Methicillin. After that, one by one oxacillin, nafcillin, cloxacillin and dicloxacillin were added in this class. Penicillins of this class don’t possess broad spectrum activity as compared to previous class of penicillin. Particularly, the antimicrobial efficacy of Penicillinase-Resistant Penicillins are aimed straightly against penicillinase-creating strains of gram (+) cocci, more specifically against staphylococcal species. For this reason, these penicillins are often called as anti-staphylococcal penicillins.
Aminopenicillins (Amoxicillin, Bacampicillin, Ampicillin)
The aminopenicillins were the first class of penicillins, which were discovered as active agents against several gram (-) bacteria (e.g. H. influenzae and E. coli). This class of penicillins have acid resistant properties, and for this reason they are available in oral dosage forms. Orally administered drugs (amoxicillin, Bacampicillin and ampicillin) of this class are usually used in several mild infections, including sinusitis, tonsillitis, otitis media, bronchitis, bacterial diarrhea and UTIs. In addition, you need to know that for the otitis media treatment, Amoxicillin is considered as the drug of choice.
Extended Spectrum Penicillins
Extended Spectrum Penicillins are also called as anti-pseudomonal penicillins. They include both acylaminopenicillins (mezlocillin, piperacillin, and azlocillin) and alpha-carboxypenicillins (ticarcillin and carbenicillin). The antibiotics of this class penicillin have similar spectrum of anti-bacterial activity as compared to aminopenicillins. However, these penicillins have an additional anti-bacterial activity against many organisms (gram-negative) of the Enterobacteriaceae family, including several strains of Pseudomonas aeruginosa. The antibiotics of this class may be administered alone or in combination with Aminoglycosides. In addition, you need to know that like the aminopenicillins, drugs of this class are also vulnerable to inactivation by beta-lactamases.
#27 Use of microorganisms to manufacture antibiotic penicillin
Antibiotics are substances which kill bacteria without harming human cells. They help to cure bacterial infections. Penicillin is made by growing the fungus Penicillium in a large fermenter.
Three colonies of a Penicillium mold growing on an agar medium.
Often, it is easier to use the whole microorganisms rather than extract its enzymes from it. The microorganism is grown in a fermenter, its enzymes convert a substrate to a desired product. The production of antibiotic penicillin is one example.
Fermenter The fungus is grown in a culture medium containing carbohydrates and amino acid. This looks like watery porridge and is stirred continuously to:
- Keep the fungus in contact with fresh supplies if nutrients.
- Mix O2 into the culture
- Roll the fungus up into little pellets (this facilitates the separating of the liquid part containing penicillin from the fungus lately).
15-24 h , the fungus just grows. After that it begins to secret
penicillin . Rate of production depends on how much sugar is available:
- A lot of sugar à not much penicillin
- No sugar à no penicillin
small amount of sugar have to be fed all the time that the fungus is producing penicillin.
The culture is kept going until the
rate of production is so
slow that is not worth waiting more (often after a week). Then it is
filtered , and the liquid is treated to
penicillin in it.
History (not included in the syllabus)
Thousands of glass fermentation vessels like this one were used in Glaxo (now GlaxoSmithKline) laboratories to produce penicillin.
The penicillium mould was grown on the surface of a liquid filled with all the nutrients it needed. This approach was replaced by the method of growing the mould within large industrial fermenters. The antibiotic was first used in the early 1940s and saved the lives of many soldiers during the Second World War.
Discovering of Penicillin
Sir Alexander Fleming, 1952 (photo AP)
Penicillin was discovered
Alexander Fleming – the Scottish bacteriologist – accidentally left a dish of staphylococcus bacteria uncovered for a few days. He returned to find the dish dotted with bacterial growth, apart from one area where a patch of
mould (Penicillin notatum) was growing. The mould produced a substance, named
penicillin by Fleming, which inhibited bacterial growth and was later found to be effective against a wide range of harmful bacteria.
However, it was not until
World War II that penicillin, the
first antibiotic, was finally isolated by Howard Florey and Ernst Chain. Fleming, Florey and Chain received a Nobel prize in 1945, for their discovery which revolutionised medicine and led to the development of lifesaving antibiotics.
Royal Society of Chemistry sciencemuseum